1. Field of the Invention
This invention is concerned with the production of heavy oil from underground deposits of tar sands.
2. Description of the Prior Art
In applicant's copending application Ser. No. 189,997, filed Sept. 23, 1980, there is disclosed a process for extracting organic matter from tar sands with liquid sulfur dioxide. The process is particularly applicable to tar sands that have been mined and transported to a plant for the extraction operation. There are, however, vast deposits of tar sands and other heavy oil reservoirs that are underground and are not susceptible to mining. For example, the Athabasca tar sands in Alberta Province, Canada, have been estimated to contain 860 billion bbls. with only 26 billion bbls. recoverable by current technology. Since the heavy oil in tar sands is highly viscous to ambient formation temperatures, it is not recoverable in its natural state through a well by ordinary production methods. Resort must be had to techniques to make the heavy oil more readily flowable, such as a suitable solvent or heat, or a combination thereof.
It has been proposed to use various water-flooding processes, including the use of aqueous solutions of sulfur dioxide, in the recovery of flowable oil from subterranean reservoirs. Insofar as is now known, however, the process of this invention for recovering heavy oil has not been proposed.